TUCSON, AZ — Summer showed up Monday in Tucson, right on time and right at 99 degrees.
High temperatures are expected to stay near to slightly above normal for most of the week, with the first real thunderstorm chances of the season arriving by Wednesday as moisture pushes in from the east.
The National Weather Service noted Monday's forecast marks Tucson's first above-normal high since May 16, and the first day of meteorological summer.
From there, temperatures should hold within a couple degrees of normal through the week before turning slightly cooler late in the week and into the weekend.
The more interesting story develops midweek. Moisture moving into New Mexico on Tuesday is expected to trigger scattered thunderstorms there, with low-level humidity spreading west into eastern parts of southeast Arizona by Tuesday night. That sets the stage for afternoon thunderstorm chances Wednesday and Thursday, mainly over the mountains of Greenlee, Graham and Cochise counties.
Wednesday looks like the most active day, with storm probabilities ranging from 10 to 60 percent depending on location, and the highest chances concentrated in the White Mountains. Eastern Pima, southeastern Pinal and Santa Cruz counties sit on the western fringe of the moisture push and could see some activity as well.
One caveat: don't count on much rain. The weather service cautioned that storms that do develop are not expected to produce a lot of rainfall, and some thunderstorms on the western edge of the moisture plume will be mainly dry.
That raises the fire weather concern familiar to anyone who has lived through an Arizona summer: lightning with little rainfall over dry terrain.
The moisture clears quickly on Friday, though storm chances may hold on a bit longer in the White Mountains. After that, dry westerly flow takes over heading into the weekend.
Looking further out, the 8-to-14-day outlook for June 8 through 14 leans above normal on temperatures, with a probability around 53 to 55 percent.
The weather service flagged June 11 through 14 as the window when the first genuinely hot temperatures of the year become possible.
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